The invention relates to a centrifugal pump impeller.
The British patent publication 575,346 A and the German patent publication 1,249,693 C describe single-piece impellers for centrifugal pumps, which operate in the range of minimum specific speeds of rotation. Such impellers have the feature that the actual vane ducts are produced by machining tools, having a straight form and along their entire length have constant circular cross section. In comparison with other known impellers with a vane duct widening like a diffusor, they have the advantage of simple manufacture but have the disadvantage of poor hydraulic efficiency.
Another design is illustrated in the Russian patent publication 620,674 A. This has a so-called open impeller, in the case of which the vane duct remains open along its entire length. It represents an unusual design to the extent that in this case the vane ducts are open drilled impeller ducts provided with a longitudinal slit. At the discharge port this design has the feature that the delivery part is made very much narrower than the vane ducts so that there are substantial pressure losses. The hydraulic efficiency is accordingly greatly impaired. Furthermore, the open impeller leads to an axial thrust towards the intake end.